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XxJF
Background: Know: encoding rules, manager , agent , atomic transactions, Recognize: Anticipates: network management protocols (SNMP & syslog), trap Tasks for NM protocols Network management protocols has three main tasks: carry content, error control and security. Moreover, the most common protocol is Simple Network Management Protocol (SNMP). '1. Carry content ' 1. Network management protocol is used to identify what is to be accessed and its value. NM protocols collect network communication information and relevant network managed devices statistic data with agent softw'ar'e. It keeps collecting data and then records the data into MIB(management information base). NM operators may get these data by sending command codes, which is called polling. NM operators can monitor network status with polling and reveal the communication trend. NM operators use interrupt-based method to collect data as well. 2. 'BER(Basic Encoding Rules) is used to encode values into strings with TLV(type-length-value) refer to (XxJ6). In ASN.1 it is also known as ITC(identifier- length-content). '''3. '''Management system uses “GET, GETNEXT and GETBULK” commands to get data. Manager(client) sends request command to agent(server) then agent replies manager with respond command. This is the way to match responses to requests. For the manager part process: translates internal data to ASN.1 format- sends request- received response PDU from agent- translates ASN.1 package to internal data format. For the agent part process: from manager- received SNMP request PDU from manager- translates ASN.1 structure to internal data- maps MIB variables to internal variables- implement SNMP request to Set or Get MIB value- translates response PDU to ASN.1 format- sends SNMP response PDU to manager. '''4. '''For the protocols & objects part, it can be shown below: Network Management System | Management applications & NM operators | NM protocols (like SNMP) | | | Agent Agent Agent | | | MIB MIB MIB | Managed objects '''5. 'TRAP or INFORM is used to report asynchronous event. TRAP: SNMP managed devices notice SNMP manager rather than waiting to be polling again. In NM system, agent can report asynchronous event to manager at anytime instead of waiting get the error data when polling. TRAP PDU: PDU type- enterprise- agent-addr- generic-trap- specific-trap- time-stamp- variable-bindings. INFORM is added in SNMPv2. '''6. IP fragmentation refers to http://www.faqs.org/rfcs/rfc1270.html. Manager/Agent must support datagram of at least 484B, SNMP avoids IP fragmentation because it increases sensitivity to loss: any fragment loss causes message damage. Refer to (Xx0Y) '2. Error control ' Error control aims to record, detect and respond the error in the network. Error control is achieved based on SNMP MIB objects. SNMP will not standardize error control if no response received within expected time. It will leave recovery from loss to implementation. For the atomic transactions, in SNMPv1, when GetRequest PDU bounding with multiple variables, agent keeps get them all or ignore all of them. '3. Security ' In SNMPv1, security was fragile because agent authorizes with unencrypted code. SNMPv2 improved the security despite of its complicated system. SNMPv3 optimized the security aspect and provided data integrity, authentication and packet encryption. Data integrity ensured the whole data was not been modified. Authentication examined whether if it came for correct source. And packet encryption avoided spying without authorization. Category:All